1. Technical Field
This document relates to devices and methods for the treatment of medical disorders including heart conditions and hypertension. For example, among other things this document relates to devices and methods for treating atrial fibrillation by performing thoracic vein ablation procedures, including pulmonary vein myocardium ablation. In some embodiments, the ablation procedures are performed in coordination with the delivery a pharmacological agent that can provide therapeutic effects such as the abatement of tissue stenosis or neointimal hyperplasia that may otherwise be caused by the ablation.
2. Background Information
Atrial fibrillation is an irregular and often rapid heart rate that commonly causes poor blood flow to the body. During atrial fibrillation, the heart's two upper chambers (the atria) beat chaotically and irregularly—out of coordination with the two lower chambers (the ventricles) of the heart. Atrial fibrillation symptoms include heart palpitations, shortness of breath, and weakness.
Ablation procedures, including ablation of thoracic veins such as the pulmonary vein, are a treatment for atrial fibrillation. During pulmonary vein ablation, catheters are inserted into the atrium. Energy is delivered from the catheter to the tissue of the pulmonary vein and/or near the ostia of the pulmonary veins in the left atrium. The energy delivered causes scarring of the tissue. The scars block impulses firing from within the pulmonary veins, thereby electrically “disconnecting” them or “isolating” them from the heart. This can provide restoration of normal heart rhythms.
However, an undesirable side effect of treatment of atrial fibrillation by pulmonary vein ablation is pulmonary vein stenosis and neointimal hyperplasia. Pulmonary vein stenosis is the narrowing of the vessels that carry blood from the lungs to the heart. Pulmonary vein stenosis can result in reduced cardiopulmonary efficiency and a decline in quality of life. In some cases, to reduce the effects of stenosis, only a partial circumference of the pulmonary vein is ablated. However, such partial-circumferential ablation procedures are generally less effective for eliminating atrial fibrillation in comparison to ablation of the entire circumference of the pulmonary veins and/or pulmonary vein ostia.
In some cases, ablation procedures can also be used advantageously in the renal arteries to treat hypertension. Ablation of the renal sympathetic nerves using catheter-delivered radiofrequency energy may be an effective intervention for uncontrolled hypertension in some instances. For example, such renal denervation procedures may be beneficial for at least some of the 20 to 30 percent of adults being treated for hypertension that do not achieve adequate blood pressure control with medications.